Grass mowing machines and other vehicles powered by internal combustion engines may be provided with hourmeters that track and display the cumulative time the engine has operated. The information may be used for a number of different purposes including vehicle warranty, service and maintenance scheduling, rental usage, or determining resale value. The following patents provide examples of hourmeters for such vehicles.
U.S. Pat. No. 4,630,292 entitled “Fuel Tax Rebate Recorder” relates to a system for recording the total time that a motor vehicle is running, including three electrically driven timers, one of which is connected in series with the oil pressure switch of the motor so that the timer is energized while the motor is running.
U.S. Pat. No. 5,337,003 entitled “Self-Contained Clip-On Engine Operating Time Log” relates to a sensor and circuitry to detect spark impulses in the ignition wire for determining the operating time of the engine.
U.S. Pat. No. 5,644,491 entitled “Self Contained Multi-Function Engine Monitor and Timer for Providing Engine Running Time, Job Time, Service Time and Tachometer Functions” relates to an engine monitor coupled to a spark pick up wire, and provides total running time, job time and service time metering
U.S. Pat. No. 5,644,551 entitled “Adaptable Engine Usage Meter” relates to a meter connected to the ignition wire of a mower engine, and mounted on a mower handlebar.
U.S. Pat. No. 6,609,357 entitled “Lawn and Garden Control Module” relates to a controller for monitoring inputs relating to status of a mower/tractor for determining a safety status condition and inhibiting operation in response to a determination of a safety status condition.
U.S. Pat. No. 6,972,668 entitled “Tamper-Evident Use-indicating Odometer and Engine-Timer” relates to a tamper evident combined odometer and engine time recorder.
Some mowing vehicle warranties may be hour-limited. However, if the hourmeter is unplugged, the engine can run without accumulating time on the hourmeter. This would allow a user to unplug the hourmeter and continue operating the lawn mower without falling out of the warranty period.
A tamper resistant hourmeter is needed for a grass mowing machine to ensure time is recorded and accumulated while the engine is running. A tamper resistant hourmeter is needed that will prevent a user from unplugging it for unrecorded use of the mower.